Our research is aimed towards isolation and characterization of lymphoid and myeloid cells at various stages of differentiation to define their antigenic determinants and their functions in cellular differentiation using an in vitro hematopoietic stem cell differentiation system. Human Ia-like antigens of p29-34 complex immunoprecipitated with the rabbit anti-p29-34 will be compared serologically and immunochemically to the unique Ia-like antigens of 100,000K isolated from myeloblasts from leukemic patients, normal T lymphocytes cultured with interleukin-2 and U937 macrophage-like cell line induced with phorbol myristate acetate. Monoclonal antibodies to p100,000 Ia-like molecule will be prepared and characterized. The possibility that p100,000 molecule immunoprecipitated with anti-p29-34 may be a precursor of conventional Ia-like antigens also will be investigated using internal labeling, chemical comparisons by tryptic peptide analysis, sequential immunoprecipitation, pulse chase and in vitro conversion experiments. The presence of this unique 100,000 dalton Ia-like antigen and other lymphoid and myeloid leukemia-associated antigens defined by available monoclonal antibodies in various stages of normal lymphoid and myeloid differentiation and leukemic disorders will be determined by immunofluorescence, cytotoxicity and immunoprecipitation analysis. In addition, monoclonal antibodies defining normal and leukemia-associated cell surface structures also will be analyzed employing in vitro marrow culture of hemopoietic stem cell differentiation in order to identify the immunobiological significance of various cell surface antigens in cellular differentiation and cooperation. The long-term goal is to elucidate the mechanisms influencing the expression of these cell surface antigens and/or receptors and understand functions of these surface proteins in normal and malignant cellular differentiation.